Should I go 10/30 or 20/20 on javelin/boltspitter Skinks?

Make 10 of both

Make 20 with boltspitters

I currently have 10 of both Skinks with javelins and boltspitters and have another box of them on the way but I'm not sure whether it would be better to add 10 to each unit to give them both +1 to hit or go all in on the Boltspitters for +2 to hit for them.